How to make my products from sub-category display in root category at Magento shopping cart?

In order to display products from sub-categories in root category at Magento you need to:

1. Login to your Magento Admin panel -> Catalog -> Manage Categories -> "Select Category" -> Display Settings -> Is Anchor = "Yes"
2. And then go to Admin -> System -> Index Management -> "Select All" -> "Reindex data" -> "Submit"